Historically, there have been developed a wide variety of enclosed spaces for facilitating the handling, inspection, analysis and/or production of various materials in a sterile and/or decontaminated environment. Examples of such enclosed spaces are (but are not limited to): microbial isolators, sterile transfer bays, industrial spaces, contained volumes, "small-transfer" microbial isolators (such as those having a volume of about 25 cubic feet), microbial isolators with large flexible work stations (such as those having a volume of between about 350 and about 400 cubic feet with two or more flexible-suit work stations), autoclave interface microbial isolators, industrial spaces that require sterilization (such as glass rooms and industrial-scale aseptic processing isolators), and sterilized enclosed spaces used in the food industry for various functions (e.g. for the sterilization of spices, flour bleaching, surface decontamination of given products, etc.).
Some known "glove-type" isolators, which provide long gloves in the shape of a human forearm and that extend inwardly from the outer surface of an isolator into the enclosed space itself, are manufactured by, for example, "la Calhene" of Velizy, France and Laminar Flow, Inc. of Ivyland, Pa. Further, "la Calhene" is known to produce half-suit isolators, such as the "series iso 2100" which involves an airtight suit in the shape of a human torso and extending arm portions, also including a helmet portion, and that extends from the bottom surface of the enclosed space and into the enclosed space itself. Several other types of enclosed spaces, including entire sterile rooms, are disclosed in "Clean Rooms" magazine, Vol. 10, No. 5, May, 1996.
Generally, two types of isolators have been available, namely those with sides or walls that may generally be regarded as "flexible" and those with sides or walls that may generally be regarded as "rigid". Historically, these have been considered as being virtually interchangeable with one another and/or equivalent in their performance, function and operation, and their use or desirability of use has often been governed by little more than considerations of cost.
Historically, in order to effect the actual sterilization or decontamination of enclosed spaces such as those described hereabove, there have been proposed numerous apparatus for providing in such enclosed spaces appropriate quantities of sterilant gas, in appropriate proportional concentrations of various compounds known to provide a sterilizing or decontaminating effect.
Recently, many efforts have focused upon: the generation of a gas or compound believed to be appropriate to help effect sterilization or decontamination within the space in question; the efficient application of such a gas or compound to the space to be sterilized or decontaminated; and the environmentally-sensitive disposal and/or recovery of such gases or compounds once they have been used for the purpose of sterilizing or decontaminating the space in question.
A need has also often been observed in connection with providing sterilization/decontamination apparatus that do not necessarily require permanent attachment to a given enclosed space, i.e., that are sufficiently portable and versatile as to be connectable or disconnectable with a single enclosed space or type of enclosed space.
Further, a need has been observed in connection with providing sterilization/decontamination apparatus that are sufficiently portable and versatile as to be connectable or disconnectable, on different occasions, with different enclosed spaces or types of enclosed spaces.
Although many different types of gases or compounds have been proposed for use as sterilants or decontaminants in the context described hereinabove, many have been found to be not as effective as desired or as not lending themselves to facilitated environmentally-safe disposal or recovery once sterilization/decontamination procedures have been completed. Over the years, the use of chlorine dioxide gas as a sterilizing agent has been widely recognized. Its use in such a capacity is described, for example, in the following U.S. Patents to Rosenblatt et al.: U.S Pat. Nos. 5,326,546; 5,290,524; 5,234,678; 5,110,580; 4,681,739 and 4,504,442. Manners of generating chlorine dioxide gas in such a capacity are also disclosed among the aforementioned patents. However, a need has been recognized to utilize chlorine dioxide gas as a sterilant in an efficient manner that provides effective sterilization or decontamination capabilities, that lends itself to facilitated exhaustion into the ambient atmosphere in an environmentally-safe manner as well as efficient recovery of a designated active ingredient or ingredients, and that can be controlled in a manner most conducive to undertaking the sterilization or decontamination task at hand.
The present discussion will now turn briefly to various subsidiary components of sterilization/decontamination apparatus, as well as processes for manipulating and/or controlling apparatus and/or their constituent components, for which particular needs have been recognized.
Sterilization/decontamination apparatus have often included, among other components, an arrangement for generating sterilant gas and an arrangement for recovering and/or exhausting used gas. "Recovery" normally involves the task of retaining at least one active ingredient of a sterilant gas once it has been used in a sterilizing procedure, while "exhausting" normally involves the environmentally-safe expulsion of used sterilant gas, or at least portions thereof, into the ambient atmosphere.
Conventionally, gas recovery systems for use in sterilization/decontamination apparatus often include arrangements in which incoming gas, that is to be exhausted or recovered, will be directed into a container that holds a "scrubber solution". In this, what may be termed a "liquid-based system", the gas is thus forced through a column of liquid having a significant hydrostatic head, so that bubbles of gas will appear shortly thereafter at the surface of the column of liquid. Conceivably, the incoming gas will have sufficiently interacted with the scrubber solution so as to have been effectively "scrubbed" or even neutralized by the time it arrives at the surface of the column of liquid. The resultant "bursting" of bubbles at the upper surface of the liquid column will then result in the further upward expulsion of "scrubbed" gas, then either to be exhausted directly into the ambient atmosphere or to be sent to a "post-scrubber" arrangement for recovery of at least one active ingredient. "Soda-lime" post-scrubbers have been used for at least the latter purpose.
Several drawbacks have been recognized in conjunction with such liquid-based systems. First, it is generally necessary to maintain a relatively large hydrostatic head of the scrubber solution within the container, in order that the incoming gas will be sufficiently "scrubbed" prior to being sent either to the ambient atmosphere and/or to a post-scrubber such as that mentioned above. Since the hydrostatic head would appear to be a critical parameter, it has often been the case that very large hydrostatic heads have been required. This, in turn, will usually present the disadvantage that a significant degree of pressure, associated with the entry of the incoming gas into the recovery system, is required in order for the gas to sufficiently progress upwardly through the liquid column in the first place. In the presence of a significantly high hydrostatic head, this pressure, often referred to as "back-pressure", can be significant, with the result that the "back-pressure" is effectively transmitted rearwardly back into the sterilization/decontamination apparatus, with the possible result of damage to valves and/or other components. It has often been found that the service life of given components in a sterilization/decontamination apparatus is effectively shortened because of such back-pressure or that very elaborate and expensive valve arrangements are required within the system in order to withstand such high degrees of back pressure. As a result of this back-pressure, it has been the case that expensive and/or bulky pumps have been required to effectively propagate the incoming gas upwardly through the column of scrubber solution.
In the context of sterilization/decontamination apparatus (and elsewhere), the importance of measuring relative concentrations of given gases and/or compounds during a sterilization/decontamination procedure has been widely recognized. Particularly, a need has been recognized in conjunction with measuring the relative concentration of "sterilant" portions of gas while being directed into and out of an enclosed space, or while in the enclosed space, in order to ensure that it falls within an acceptable range. Furthermore, many conventional measuring devices lack the capability to be utilized for more than one specific, predetermined purpose. Therefore, a need has been recognized for versatile gas measurement devices that eliminate the deficiencies associated with conventional measurement devices.
Historically, a wide range of control valves have been used in conjunction with sterilization/decontamination apparatus. However, many of the valves proposed to date have been relatively complex, expensive and not reliably hermetically tight. Therefore, a need has arisen for the provision of simple, inexpensive and hermetically tight valves both in the context of sterilization sciences and elsewhere.
A need exists for other simple and inexpensive valving systems and/or valve operation schemes, particularly in the context of inflating and deflating sterilization/decontamination spaces (particularly if the walls are flexible) or at least flushing enclosed spaces, introducing sterilant gas into such spaces and subsequently extracting the sterilant gas.
In the context of sterilization/decontamination apparatus, there has also historically been a need for effective software or other programming logic capable of effectively controlling the components and sub-components of the apparatus.
In this context, a particular need has arisen in conjunction with permitting the admission of a sterilant gas into an isolator (or other enclosed space) under controlled conditions for a defined period of time. In this vein, difficulties have often been encountered in defining, planning and programming any software or programming logic that may be required to bring a new sterilization/decontamination apparatus on-line (i.e., to establish its operating parameters in such a manner that it is able to effectively perform a sterilizing or decontaminating process). A need has also arisen in conjunction with modifying any existing control programs (or programming logic) to accommodate any new control functions or new operating environments and also "validating" a sterilization/decontamination apparatus on-line (i.e., to establish "worst-case" operating parameters in such a manner that it is able to demonstrate and verify that the system can effectively perform a sterilizing or decontaminating process under "worst-case" conditions).
Finally, many problems have been observed to date, in conventional sterilization/decontamination apparatus, in conjunction with properly "charging" the circulating air/gas in the apparatus so as to accurately infuse proper concentrations of sterilant gas into the system at start-up. Particularly, in the past, many conventional apparatus have based "charging" on direct measurement of gas concentration in the enclosed space to be sterilized or decontaminated. However, such direct measurements are only accurate after the sterilant gas has uniformly distributed throughout the enclosed space. Thus, valuable time is often wasted while awaiting a state in which accurate measurements can be taken. Accordingly, any attempt to continue a sterilizing process before such a state has been achieved could result in inaccurate measurements. Further, many conventional sterilizing or decontaminating processes have estimated gas concentrations at "charging" based on pressure change within the enclosed space, which is an indirect and thus potentially inaccurate estimate of the concentration, or even the mere presence, of sterilant gas in the enclosed space. Finally, many spaces which are to be sterilized or decontaminated cannot be evacuated and have required manual sterilization or decontamination, thus involving potentially significant expenditures of human time and effort and introducing the potentially harmful risk of human error.